Exhaust silencer unit for propulsion unit

Abstract

A number of embodiments of exhaust silencers for marine propulsion units including an exhaust device having a first expansion chamber, a pair of second expansion chambers and a third expansion chamber all formed within a common housing. The flow of exhaust gases is from the exhaust of the engine into the first expansion chamber, directly from the first expansion chamber into each of the pair of second expansion chambers and directly from the second expansion chambers to the third expansion chamber. In all embodiments the flow from the second expansion chambers to the third expansion chamber is in confronting relationships so as to improve silencing. In one embodiment, the second expansion chambers have different effective volumes so as to provide an extended range of tuning for the silencing.

We claim: 
     
       1. An exhaust silencer for exhaust gases of an internal combustion engine comprising a common housing defining a first expansion chamber, an exhaust inlet for delivering exhaust gases from said engine into said first expansion chamber, a pair of spaced apart second expansion chambers, restricted flow means for communicating said first expansion chamber directly with each of said pair of second expansion chambers for successive expansion contraction and expansion of the exhaust gases flowing therebetween, a third expansion chamber, restricted flow means communicating each of said second expansion chambers directly with said third expansion chamber for successive expansion contraction and expansion of the exhaust gases flowing therebetween, and means for discharging exhaust gases from said third expansion chamber to the atmosphere, said pair of second expansion chambers being disposed on and extending along opposite sides of said third expansion chamber. 
     
     
       2. An exhaust silencer as set forth in claim 1 wherein the first expansion chamber is disposed adjacent one side of the pair of second expansion chambers and the third expansion chamber. 
     
     
       3. An exhaust silencer as set forth in claim 2 wherein the restricted flow means for communicating the first expansion chamber with the pair of second expansion chambers comprise a pair of apertures formed in a wall separating the first expansion chamber from the second expansion chambers at the upper end thereof. 
     
     
       4. An exhaust silencer as set forth in claim 3 wherein the restricted flow means for communicating each of the second expansion chambers with the third expansion chamber comprises a pair of openings formed in the upper end of walls separating each of the second expansion chambers from the third expansion chamber. 
     
     
       5. An exhaust silencer as set forth in claim 4 wherein the openings are in facing relationship. 
     
     
       6. An exhaust silencer as set forth in claim 5 wherein water is delivered along with the exhaust gases to the exhaust silencer and wherein the walls are formed with small weep holes at the lower ends thereof for communicating the expansion chambers with each other and permitting water to flow therebetween to maintain substantially constant volume for the respective expansion chambers. 
     
     
       7. An exhaust silencer for exhaust gases of an internal combustion engine comprising a first expansion chamber, an exhaust inlet for delivering exhaust gases from said engine into said first expansion chamber, a pair of spaced apart second expansion chambers, means for communicating said first expansion chamber directly with each of said pair of second expansion chambers, a third expansion chamber disposed between said pair of second expansion chambers, means communicating each of said second expansion chambers directly with said third expansion chamber, and means for discharging exhaust gases from said third expansion chamber to the atmosphere, said expansion chambers all being formed in a common housing with the first expansion chamber disposed adjacent one side of said pair of second expansion chambers and said third expansion chamber, said means for communicating said first expansion chamber with said pair of second expansion chambers comprise a pair of apertures formed in a wall separating the first expansion chamber from the second expansion chambers at the upper end thereof. 
     
     
       8. An exhaust silencer as set forth in claim 7 wherein the means for communicating each of the second expansion chambers with the third expansion chamber comprises a pair of openings formed in the upper end of walls separating each of the second expansion chambers from the third expansion chamber. 
     
     
       9. An exhaust silencer as set forth in claim 8 wherein the openings are in facing relationship. 
     
     
       10. An exhaust silencer as set forth in claim 9 wherein water is delivered along with the exhaust bases to the exhaust silencer and wherein the walls are formed with small weep holes at the lower ends thereof for communicating the expansion chambers with each other and permitting water to flow therebetween to maintain substantially constant volume for the respective expansion chambers. 
     
     
       11. An exhaust silencer for support as a unit within a hull of a watercraft for silencing exhaust gases of a separate internal combustion engine supported within the hull at a location spaced from said exhaust silencer comprising a first expansion chamber, an exhaust inlet for delivering exhaust gases into said first expansion chamber, flexible conduit means for delivering exhaust gases from said inlet across said hull to said exhaust inlet, a pair of spaced apart second expansion chambers, means for communicating said first expansion chamber directly with each of said pair of second expansion chambers, a third expansion chamber, means communicating each of said second expansion chambers directly with said third expansion chamber, said expansion chambers all being formed in a common housing, and conduit means for discharging exhaust gases from said third expansion chamber to the atmosphere through the hull of said watercraft. 
     
     
       12. An exhaust silencer as set forth in claim 11 wherein the pair of second expansion chambers are disposed on opposite sides of the third expansion chamber. 
     
     
       13. An exhaust silencer as set forth in claim 12 wherein the first expansion chamber is disposed adjacent one side of the pair of second expansion chambers and the third expansion chamber. 
     
     
       14. An exhaust silencer as set forth in claim 13 wherein the means for communicating the first expansion chamber with the pair of second expansion chambers comprises a pair of apertures formed in wall separating the first expansion chamber from the second expansion chambers at the upper end thereof. 
     
     
       15. An exhaust silencer as set forth in claim 14 wherein the means for communicating each of the second expansion chambers with the third expansion chamber comprises a pair of openings formed in the upper end of walls separating each of the second expansion chambers form the third expansion chamber. 
     
     
       16. An exhaust silencer as set forth in claim 15 wherein the openings are in facing relationship. 
     
     
       17. An exhaust silencer as set forth in claim 16 wherein water is delivered along with the exhaust gases to the exhaust silencer and wherein the walls are formed with small weep holes at the lower ends thereof for communicating the expansion chambers with each other and permitting water to flow therebetween to maintain substantially constant volume for the respective expansion chambers. 
     
     
       18. An exhaust silencer as set forth in claim 11 wherein the pair of second expansion chambers are disposed on opposite sides of the third expansion chamber. 
     
     
       19. An exhaust silencer as set forth in claim 18 wherein the first expansion chamber is disposed adjacent one side of the pair of second expansion chambers and the third expansion chamber. 
     
     
       20. An exhaust silencer as set forth in claim 11 wherein the means communicating the second pair of expansion chambers with the third expansion chamber comprise facing openings wherein the flow of exhaust gases from the second expansion chambers to the third expansion chamber is confronting relationship. 
     
     
       21. An exhaust silencer as set forth in claim 11 wherein the second expansion chambers have different effective volumes. 
     
     
       22. An exhaust silencer as set forth in claim 21 wherein the length of the flow from the first expansion chamber through one of the second expansion chambers to the third expansion chamber is longer than the flow from the first expansion chamber through the other of the second expansion chambers to the third expansion chamber. 
     
     
       23. An exhaust silencer as set forth in claim 11 wherein water is delivered to the exhaust silencer along with the exhaust gases and wherein means for communicating at least one of the expansion chambers with another of the expansion chambers comprises a number of relatively small orifices through which the water will be atomized as it flows therethrough with the exhaust gases for improving the water exhaust gas contact.